SUSPENSION
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Porsche Boxster Suspension

The Porsche Boxster suspension is generally quite reliable. There are 3 common failure points or problem areas which its worth checking for from time to time.

1. Lower track crontrol arms - these have a suspension bush which fails and can cause initially a squeeking noise, increased tyre wear and eventually cause a knocking noise over bumpy surfaces.

2. Broken coil springs - The tip breaks off of the coil springs very occasionally on Boxsters, this can cause the springs to not seat properly and cause a groaning noise when turning the steering and occasionally a clicking or knocking noise over very bumpy roads.

3. Leaking/worn out shock absorbers - This happens with age and wear, like any car. Leaking can be seen my damp oily fluid being found on the shock absorbers, and wear can often be seen my movement between the shock absorber shaft and the body of the shock absorber. Normally if the shock wears out, you will also see a leak. So its best just to keep your eyes peeled for damp oily gritty substance around your shock absorbers.

All of these problem areas are repaired by simply replacing the offending item.

What parts make up the suspension on a Porsche Boxster?

The Porsche Boxster is fitted with an industry standard form of suspension system known as McPherson struts.

Here is a diagram showing the assembly of components which make one of these struts.

As you can see, one of these "struts" is made of several components.

Suspension Damper - Also known as the suspension strut, or Shock absorber. This components job is to tie the entire suspension strut together. It also has an inner shaft which is there to control the "bounce" or "rebound" of the suspension. Without this, if the car was just mounted on springs, the car would bounce after hitting a bump, its there to control the absorbing of shocks as you hit pot holes or to stop the car bouncing high in the air following hitting the ground after a bridge or ramp.

Coil Spring - The job of this component is to offer resistance to gravity and to absorb shocks as you drive over bumps in the road and then try to return the car back to a safe riding height afterwards.

Bellows - Like all bellows on a Boxster, its job is to cut down the volume of dust and grit which may otherwise scratch and damage the shock absorbers shaft.

Top Mount- this is the part which connects to the bodywork of the car and also allows the shock absorber to twist (on the front end of the car so you can steer) and to move freely at angles as the assembly expands and contracts as you drive over bumps.

 

Connecting the bottom of the shock absorber to the wheel is a hub as you can see bellow.

The hub assembly consists of the following parts.

Hub Upright - Also known as a stub axle, this part is designed to contain the wheel bearing and be the central mounting part to house the wheel bearing assembly, shaft and Hub. It connects to the suspension strut and to the lower control arm.

Wheel Bearing - I think everyone knows what one of these is, but it basicly has an outer surface which remains still within the hub, while and inner tube is free to spin on a series of bearings. The shaft and hub rotate within this bearings and therefore allow your wheels to turn without the strut also turning!

Shaft - This allows the hub to be held and not pulled through the wheel bearing. On the rear of a Boxster this shaft is connected to the driveshaft to allow power to be transmitted to the rear wheels via the hub.

Retaining Plate - This part stops the wheel bearing wandering out of the hub assembly and leaving you with only 3 wheels when your going 100 mph!

Hub - This is the part that the brake disk and wheel attatch to.

 

Then last of all in the sequence of suspension parts you have the crossmember and track control arms.

The cross member has a very simple job. It is there to create a fixed a stable distance between the suspension lower components either side of the car.

Track control arm - This part is what links the Hub upright to the cross member. This part has a suspension bush in the middle of it which has a habbit of breaking up with age, first causing a squeeking noise and eventually a clunking noise.

There is also a ball joint on the suspension arm - these rarely have a chance to fail as the bush normally fails soonest, but is only a part you can buy as an entire arm from Porsche.

The Suspension arm - this braces the track control arm to stop it being able to move in a backwards or forwards direction, and so keeping your road wheel in the middle of the wheel arch under braking etc. This part also has a suspension bush. But its less prone to failure as the track control arm.

 

Then we move onto the last suspension component. The anti roll bar.

The anti roll bar connects to the body of the car via two mountings and two bushes.

The outer ends of the anti roll bar is mounted to the suspension struts via two drop links.

The job of the anti roll bar is to keep the car level and flat as it goes through corners. It does this because for the car to tilt as it corners one strut would have to go up and the other one goes down. With the anti roll bar if this happens the bar has to twist, which it naturally tries to avoid, so helping the car remain flat through cornering.

 

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